Get last field using awk substr

Use the fact that awk splits the lines in fields based on a field separator, that you can define. Hence, defining the field separator to / you can say:

awk -F "/" '{print $NF}' input

as NF refers to the number of fields of the current record, printing $NF means printing the last one.

So given a file like this:

/home/parent/child1/child2/child3/filename
/home/parent/child1/child2/filename
/home/parent/child1/filename

This would be the output:

$ awk -F"/" '{print $NF}' file
filename
filename
filename

In this case it is better to use basename instead of awk:

 $ basename /home/parent/child1/child2/filename
 filename

If you're open to a Perl solution, here one similar to fedorqui's awk solution:

perl -F/ -lane 'print $F[-1]' input

-F/ specifies / as the field separator
$F[-1] is the last element in the @F autosplit array

Another option is to use bash parameter substitution.

$ foo="/home/parent/child/filename"
$ echo ${foo##*/}
filename
$ foo="/home/parent/child/child2/filename"
$ echo ${foo##*/}
filename